Inhibitors mitigate N2O emissions more effectively than biochar: A global perspective

Farmlands receive large amounts of nitrogen (N) from anthropogenic activities, which increase N2O emissions and promote crop productivity. Inhibitor or biochar applications have proven effective in reducing N2O emissions and promoting crop yields worldwide. However, a direct comparison of the response of N2O emissions and crop yields to inhibitor and biochar applications has not been performed. Here, we conducted a meta-analysis of 787 datasets from different locations worldwide to investigate the response of N2O emissions and crop yields to inhibitor or biochar applications for different climate factors and experimental conditions and determine the key influencing factors. We found that inhibitor applications (37.4 %) resulted in larger N2O emission reductions than biochar applications (20.2 %), but there was no difference in the crop yield improvement (5.8 % and 5.4 %, respectively). Nitrification inhibitor (NI) applications reduced N2O emissions by 40.8 %, a larger reduction than that of urease inhibitor (UI) applications (24.3 %) and the combination of NI and UI applications (36.4 %); 3,4-dimethylpyrazole succinic (DMPSA) was the most effective NI in reducing N2O emissions (50.7 %). We also found that NI applications were more effective in reducing N2O emissions than biochar applications in different climates and experimental conditions (N source, N rate, cropland type, and soil texture). In addition, the N rate was the most important factor impacting N2O emissions and crop yields when inhibitors were applied, whereas the experimental duration had the largest influence on N2O emissions under biochar applications. Moreover, soil factors were also related to N2O emissions under biochar applications or inhibitor applications. Our findings indicate that inhibitors are more effective in reducing N2O emissions than biochar worldwide.